Zeolite/alumina catalyst support compositions and method of making the same

Abstract

Zeolite/alumina composite, and a method for making, the composite for use as a catalyst substrate or catalyst carrier and comprising zeolite having a silica/alumina ratio of greater than 300 and gamma alumina having a specific surface area of greater than 100 m2/g. The zeolite/alumina composite exhibits a modulus of rupture of at least 750 psi. Additionally, the invention is also directed at a three catalyst (TWC) system for use in the removal of hydrocarbons, carbon monoxide and oxides of nitrogen from waste gas, the TWC system comprising the following components: (1) a zeolite/alumina composite catalyst support exhibiting a modulus of rupture of at least 750 psi and having a zeolite with a silica/zeolite ratio of at least 300 and the alumina comprising a gamma alumina having a specific surface area of greater than 100 m2/g; and, (2) a noble metal catalyst impregnated on the catalyst support, the noble metal selected from the group consisting of platinum, rhodium, iridium and palladium.

We claim:  
     
       1. A zeolite/alumina composite for use as a catalyst substrate or catalyst carrier consisting essentially, in parts by weight, of about 30-70 parts of high-silica zeolite having a silica/alumina ratio of greater than 300:1, and 30-70 parts of gamma alumina or stabilized gamma alumina having a specific surface area of greater than 100 m 2 /g, and, optionally, up to 30% by weight of stabilized zirconia oxygen storage material, the composite exhibiting a modulus of rupture of at least 750 psi, a specific surface area of greater than 100 m 2 /g, and being substantially free of silica binder material. 
     
     
       2. A zeolite/alumina composite as claimed in  claim 1  wherein the composite exhibits a modulus of rupture of at least 1000 psi. 
     
     
       3. A zeolite/alumina composite as claimed in  claim 1  wherein the composite exhibits a surface area of at least 200 m 2 /g. 
     
     
       4. A zeolite/alumina composite as claimed in  claim 1  wherein the composite exhibits a thermal expansion of less than about 5×10 −6 /°C. 
     
     
       5. A zeolite/alumina composite as claimed in  claim 1  wherein the composite exhibits thermal stability at a temperature up to at least 1000° C. 
     
     
       6. A zeolite/alumina composite as claimed in  claim 1  wherein the zeolite/alumina composite is honeycomb structure exhibiting at least 600 cells/in 2 . 
     
     
       7. A zeolite/alumina composite as claimed in  claim 1  wherein the stabilized zirconia includes a dopant selected from the group consisting of cerium oxide, titanium oxide, yttrium oxide, magnesium oxide, praseodymium oxide, calcium oxide, magnesium oxide, barium oxide, and mixtures thereof. 
     
     
       8. A zeolite/alumina composite as claimed in  claim 7  wherein the stabilized zirconia includes a dopant mixture comprising up to about 80%, by weight cerium oxide and up to about 20%, by weight yttrium oxide, based on the total amount zirconia. 
     
     
       9. A zeolite/alumina composite as claimed in  claim 1  wherein the alumina includes a stabilizing agent selected from the group consisting of lanthanum oxide, barium oxide, strontium oxide and yttrium oxide.